The present invention relates to a method for adjusting the flow quantity in a fuel injector.
From German Patent No. 40 25 945, a method is already known for adjusting the static fuel quantity that is spray-discharged in the stationary opening state of a fuel injector. In this context, the fuel quantity delivered is first measured when the fuel injector is open. Subsequently, the position of a perforated disk, having at least two metering openings and arranged downstream of the valve seat, is changed, as a result of which the vacant flow-cross-sections of the individual metering openings are varied. This shift in position lasts until the actual quantity discharged coincides with the stipulated setpoint quantity. The perforated disk is subsequently fixed in this position.
In addition, from DT 2 045 596 A1, it is already known to deform at least one swirl channel on a fuel injector. The swirl channel provided on a valve seat body is gradually narrowed in its flow-through cross-section by deformation until the flow quantity in the swirl channel has attained a preestablished setpoint value. The deformation is carried out by a press ram, which is introduced into the nozzle body in the downstream direction. By rotating the press ram, the cross-section of the swirl channel on the valve seat is reduced.
From U.S. Pat. No. 5,570,841, a fuel injector is already known that has a multiple-disk perforated disk. In this context, one disk of this atomization attachment in disk form has a contour for generating a swirl in the fuel to be spray-discharged. The flow, i.e., the flow quantity, of fuel through the perforated disk is set by the cross-sections of the individual swirl channels and cannot be changed.
From German Published Patent Application No. 197 24 075, a method is already known for manufacturing perforated disks for injectors. In this context, it is a question of so-called sheet-metal-laminate perforated disks, in which at least two thin sheet-metal layers are applied one on top of the other. Each sheet-metal layer of a perforated disk of this type has a different opening geometry, the openings being introduced already before the sheet-metal layers are placed on top of each other. Here too, the cross-sections of the openings determine the through-flow of the fuel and cannot subsequently be changed.
The method according to the present invention for adjusting the flow quantity in a fuel injector has the advantage that it makes it possible, in a simple manner, in a fully assembled fuel injector, to change a multilayer, or multiple-disk, perforated disk in its opening cross-sections, as a result of which the flow quantities to be discharged can be adjusted very simply even in fuel injectors having perforated disks of this type.
It is especially advantageous to execute the perforated disk as a swirl disk, especially as a so-called sheet-metal-laminate swirl disk, at least one central layer of the perforated disk having an opening contour having swirl channels and a swirl chamber. Ideally, the flow quantity is adjusted by the perforated disk, such that the deformation of the lower layer of the perforated disk is carried out in the area of at least one swirl channel, so that material of the base layer is shifted into the vacant flow-cross-section of the at least one swirl channel. Using a plurality of deformation rams for the deformation tool, it is advantageously possible to change the vacant flow-cross-section of a multiplicity of swirl channels simultaneously.
It is particularly advantageous to carry out the flow measurement of the fuel through the perforated disk immediately during the deformation process. In this way, the time used for adjusting the flow quantity is kept to a minimum.
For deforming the lower base layer of the perforated disk, a deformation tool is advantageously used which includes a stationary tool part as the perforated disk receptacle and at least one movable tool part in the form of a deformation ram.